Your budget has gone for a toss and you need to buy a graphics card. Or maybe you want to experience 4K without all the eye candy. There is a way, infact, there are 5 ways under 5,000.
It doesn't get any better than this when Rs.5,000 is all that you can put down at the moment.
Like all the cards mentioned in this list, this one also requires no external power and is the best card you can get from AMD's lineup in the price range.
So the GT 640 is stretching your budget a little. Worry not, the GT 630 is just as good but you need the Kepler version if you want to get 4K, otherwise it's limited to 2560 x 1600.
If the HD 7750 isn't within your budget then you can go for the HD 6670. With 32 stream processors lesser than the former, it isn't that behind the newer generation GPU.
You can't go lower than this. Doing so makes absolutely no sense since the returns dimish really quickly.